On FamilySearch there is a catalog for the library under the search section. That will let you know if each film in on site, digital access or in the vault. A majority of films are either at the FHL or digital access (depending on the collection you may still have to be at the FHL or a FamilySearch library to access). Occasionally (but rarely) there are films you need from the vault, you can either request these online or in person at the FHL. It usually takes a few days to 2 weeks but often you can ask them to email or contact you when the film has arrived. But, like I said, this is a rare occurrence.
No, not if it is on site
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